It is not possible to use c-mount lenses on a Canon EOS without optical adapter and without looking the mirror and insert the lens into the camera for work on infinity.
C-mount has as flange back distance 17.526 mm - and Canon EOS 44,0 mm, so the lens has tor protrude 26 mm from the C-Mount flange + ~ 5 mm for the c-mount screw + probably some more millimeters - for infinity.
For makro work you could probably tinker a cheap adapter out of an camera cap. Depending on the lens and magnification one probably gets even full frame images.
A further possibility is to adapt the c-mount lens with a optical adapter. For this you take the virtual image of the lens an enlarge it onto the Canon sensor. Probably you need a added field lens for that.
Those optical adapters are not sold, as far as I know.
I build one for tests, with a macro lens and extension rings.
The other way round, from a lens with larger image diameters to a smaller camera sensor is also possible, currently I do a little testing with a Zenitar 16 mm on my crop camera - with the full image diamter.
--
Camera DIY repair and modification linklist:
http://4photos.de/camera-diy/index-en.html